Thesis-1998-Saunders.pdf (6.95 MB)
The performance evaluation of lithium thionyl chloride batteries for long-life meter applications
thesis
posted on 2013-12-17, 14:11 authored by Tim G. SaundersA research project has been carried out to provide BG plc with service life predictions
of lithium primary batteries capable of supplying a continuous pulsed power supply to
two new electronic domestic gas meters over a desired design life of 11.5 years, in UK
weather conditions. The paper study includes investigations of the range of suitable
lithium technologies and test methods, and detailed reviews of the discharge
processes, polarisation and self-discharge failure modes of the lithium thionyl chloride
system.
A new multi-channel load test rig and a high resolution measurement system, and
software analysis tools were designed and constructed, and some 440 accelerated
discharge tests were carried out at different stress levels on 4 cell types. The results
provide a unique database of the voltage/temperature/load trends through discharge,
and generate a ranking order of performance. Basic statistical analyses have been
carried out to quantify the variability of performance trends. A hitherto unreported
behaviour pattern is characterised. Qualitative models are postulated to account for
deviations from normal behaviour exhibited by two cell types. The analysis suggests
that catholyte additives could predispose a system to early failure (due to modification
of the crystal structure of the reaction products), and that manufacturing tolerances
define the degree of failure.
Mathematical models of self-discharge rate for both low and medium rate discharge
were developed from laboratory measurements. Meter load profiles were also
measured, which together with the self-discharge model enabled prediction of
operational energy utilisation rates. A sample of 50 batteries was extracted from customers homes, after operating in the
field for periods of up to 2 years, and the battery capacity loss rates were measured by
the residual capacity method. A comparison of predicted and actual capacity
utilisation rates yielded a discrepancy of approximately 1.28. Analysis implied that
the source of the discrepancy could be adduced to an under estimate of the impact of
self-discharge, but that a factor of up to six times the predicted value was required.
Evidence was provided to show that self-discharge rate under operational stresses
could be significantly higher than that under the steady-state laboratory measurement
conditions, but that that the amplitude and time constant associated with a selfdischarge
peak was unknown and not predictable.
Mean service lives of 14 and 10 years for the respective battery types in the two types
of meter are predicted, the worst case (probability of 0.13% of the population) being
failure within approximately 5.9 years.
History
School
- Science
Department
- Chemistry
Publisher
© Tim G. SaundersPublication date
1998Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en